The invention relates to a road roller or compactor comprising at least one roller wheel unit or drum unit in which a cylindrical drum is rotationally mounted about its axle, the at least one drum unit being rotationally mounted about a steering axis on a chassis frame of the compactor.
Such compactors are known and find application more particularly on road construction sites. For steering, the complete drum unit is turned relative to the chassis frame. For this purpose the drum unit is fitted rotative to the chassis frame via articulation joints requiring maintenance. The assembly is bulky and requires continuous lubrication. The drawbacks are the costs involved as well as the bulky design and maintenance due to the continuous lubrication requirement.
The object of the present invention is thus to provide a compactor comprising a simple, cost-effective and compact articulation joint for the drum unit on the chassis frame.
In accordance with the invention this object is achieved in that the drum unit is connected to a middle piece rotationally mounted via two opposing maintenance-free angular-contact articulation joints about the steering axis on two trunnions non-rotatively connected to a mounting fixture on the chassis frame.
Making use of maintenance-free articulation joints makes it possible to do away with the need for continuous lubrication as provided hitherto. The articulation joints are supported between the middle piece and the trunnions and have no contact with the mounting fixture on the chassis frame or the drum unit itself, thus enabling the middle piece and the trunnions to be machined with high precision independently of the other components, i.e. complicated means are now no longer needed at the mounting fixture or drum unit. The result is a straightforward and compact configuration.
Furthermore, by making use of angular-contact articulation joints an O arrangement of the joints is made possible to thus enable the supporting spacing of the joints to be elevated to more than the actual spacing. In addition, the joints can be counterbraced to make for added life.
Advantageous further embodiments and aspects of the invention read from the sub-claims.
In one advantageous aspect the angular-contact articulation joints are inserted in joint openings of the middle piece and the trunnions engage inner rings of the angular-contact articulation joints. Of advantage is the simple configuration of this structure, i.e. it merely being necessary to provide the middle piece with the joint openings whilst the trunnions can be produced separately. The expense and volume of the machining required is less than when making use of a middle piece in the form of a trunnion spider.
It is of advantage to support one of the angular-contact articulation joints on the middle piece by a spring element, more particularly by a disk spring. This spring element provides, on the one hand, vibration damping and makes it possible, on the other, to install the opposing angular-contact articulation joints with zero clearance.
Preference is given to disk springs because of the high spring capacity they provide.
In accordance with one further embodiment the mounting fixture comprises a substantially rectangular chassis frame into which the middle piece is insertable, the frame being provided with two opposing openings through which the trunnions engage the angular-contact articulation joints at the middle piece. For assembly the middle piece is simply inserted into the frame. Subsequently the trunnions are inserted at opposing ends through the openings in the frame into the angular contact articulation joints. Implementing assembly is speedy and simple.
To advantage the trunnions comprise a flange for bolting to the frame of the mounting fixture to thus permit speedy and simple attachment of the trunnions. At the same time the opposing angular-contact articulation joints are reliably held in place by the likewise opposing trunnions and can be counterbraced.
In another advantageous aspect the drum unit comprises two struts, on which the drum is mounted for rotation about its axle, as well as two steering brackets for connecting the struts releasably connected thereto and connected to the middle piece. The struts and steering brackets may be configured mirror-inverse to thus simplify the design. The releasable connection between the steering brackets and struts as well as between the steering brackets and middle piece permit simple, uncomplicated assembly.
In a first advantageous embodiment the middle piece is configured substantially cylindrical and rigidly connected to a plate bolted to the steering brackets of the drum unit. This embodiment ensures that the drum unit is rotatable only about the steering axis provided and reliably excludes any other movement. Securing the steering brackets of the drum unit by bolts serves to facilitate assembly.
In a second advantageous embodiment the middle piece is configured substantially cuboidal and comprises two further maintenance-free angular-contact articulation joints with assigned trunnions arranged at right angles to the first angular-contact articulation joints. In this embodiment the trunnions pass through the steering brackets of the drum unit and are non-rotatively secured thereto. This embodiment permits in addition to rotation about the steering axis also a rotation of the drum unit about a swing axis oriented perpendicular to the steering axis. Preferably the oscillation axis is oriented parallel to the steering axis of the compactor.
This embodiment permits, in addition to a steering movement, also oscillation of the drum unit in adapting to ground irregularities and for compensating skew settings.
Advantageously at least one of these further angular-contact articulation joints is supported by a ring for tolerance compensation. This support enables inaccuracies in machining to be offset so that the spacing between the angular-contact articulation joints and the trunnions can be adapted to the spacing between the steering brackets.
When making use of such rings on both angular-contact articulation joints the location of the steering brackets may also be varied relative to the middle piece.
It is, of course, just as possible that the compactor comprises two drum units, it being preferred in this case when the mounting fixtures for the drum units are configured identical to reduce structural complexity.
In this case it is of advantage when the front drum unit is frame mounted via a cylindrical middle piece and the rear drum unit via a cuboidal middle piece so that both drum units are steerable whilst the rear drum unit is simultaneously rotatable about the oscillation axis relative to the front drum unit to thus achieve a compensation between the front and rear drum unit to avoid prohibitively high forces being introduced into the chassis frame of the compactor. This compensation is particularly important when the front and rear drums roll over planes inclined to each other.